1. Field of the Invention
The present invention relates to a semiconductor pressure sensor and manufacturing method thereof and, more specifically, to a semiconductor pressure sensor capable of temperature compensation and manufacturing method thereof.
2. Description of the Background Art
In a conventional semiconductor pressure sensor, a diffusion resistance that will be a gauge resistance, is formed in a silicon substrate. A plurality of gauge resistances are bridge-connected by diffusion interconnections of low resistance. A diaphragm is formed by etching from a rear surface of the silicon substrate. Gauge resistances are arranged at an edge portion of the diaphragm.
By way of example, Japanese Utility Model Laying-Open No. 63-178353 describes a semiconductor pressure sensor having a diaphragm formed of an oxide film, a polysilicon substrate, an oxide film and a gauge, formed on a silicon substrate with a through hole.
Further, Japanese Patent Laying-Open No. 63-042179 describes a semiconductor strain detector having a semiconductor strain gauge formed on a semi-insulating polysilicon substrate having a thin portion as a diaphragm.
Further, Japanese Patent Laying-Open No. 60-259922 describes formation of a temperature-sensitive resistor formed of the same material as a strain-sensitive resistor, at a portion free from any strain on the diaphragm in a temperature-compensated strain sensor.
In a semiconductor pressure sensor, a gauge resistance is formed on a diaphragm. When pressure is applied to the semiconductor pressure sensor, the diaphragm deforms, and resistance value of gauge resistance changes. By detecting the change in resistance value of the gauge resistance, change in pressure can be measured. Further, in the semiconductor pressure sensor, the resistance value of gauge resistance formed on the diaphragm is influenced by the temperature at the time of pressure measurement. Therefore, for accurate pressure measurement, it is desirable to eliminate temperature dependency of semiconductor pressure sensor by temperature compensation.
In the strain sensor described in Japanese Patent Laying-Open No. 60-259922, the temperature-sensitive resistor is simply provided separate from the strain-sensitive resistor at a portion free from strain on the diaphragm and, therefore, accurate temperature compensation is difficult.